Chapter DHS 157

DHS 157.03(322) (322) “Scan increment” means the amount of relative displacement of the patient with respect to the CT x-ray system between successive scans measured along the direction of such displacement.

DHS 157.03(323) (323) “Scan sequence” means a pre-selected set of 2 or more scans performed consecutively under pre-selected CT conditions of operation.

DHS 157.03(324) (324) “Scan time” means the period of time between the beginning and end of x-ray transmission data accumulation for a single scan.

DHS 157.03(325) (325) “Scattered radiation” means ionizing radiation emitted by interaction of ionizing radiation with matter, the interaction being accompanied by a change in direction of the radiation.

DHS 157.03(326) (326) “SCO-I” means a surface contaminated object (SCO) for which all of the following apply:

DHS 157.03(326)(a) (a) The non-fixed contamination on the accessible surface averaged over 300 cm2 (or the area of the surface if less than 300 cm2) does not exceed 4 Bq/cm2 (10 -4  microcurie/cm2) for beta and gamma and low toxicity alpha emitters, or 0.4 Bq/cm2 (10-5 microcurie/cm2) for all other alpha emitters.

DHS 157.03(326)(b) (b) The fixed contamination on the accessible surface averaged over 300 cm2 (or the area of the surface if less than 300 cm2) does not exceed 4x104 Bq/cm2 (1.0 microcurie/cm2) for beta and gamma and low toxicity alpha emitters, or 4x103 Bq/cm2 (0.1 microcurie/cm2) for all other alpha emitters.

DHS 157.03(326)(c) (c) The non-fixed contamination plus the fixed contamination on the inaccessible surface averaged over 300 cm2 (or the area of the surface if less than 300 cm2) does not exceed 4x104 Bq/cm2 (1.0 microcurie/cm2) for beta and gamma and low toxicity alpha emitters, or 4x103 Bq/cm2 (0.1 microcurie/cm2) for all other alpha emitters.

DHS 157.03(327) (327) “SCO-II” means a surface contaminated object (SCO) for which the limits for SCO-1 are exceeded and on which all of the following apply:

DHS 157.03(327)(a) (a) The non-fixed contamination on the accessible surface averaged over 300 cm2 (or the area of the surface if less than 300 cm2) does not exceed 400 Bq/cm2 (10 -2 microcurie/cm2) for beta and gamma and low toxicity alpha emitters, or 40 Bq/cm2 (10 -3 microcurie/cm2) for all other alpha emitters.

DHS 157.03(327)(b) (b) The fixed contamination on the accessible surface averaged over 300 cm2 (or the area of the surface if less than 300 cm2) does not exceed 8x105 Bq/cm2 (20 microcurie/cm2) for beta and gamma and low toxicity alpha emitters, or 8x104 Bq/cm2 (2 microcurie/cm2) for all other alpha emitters.

DHS 157.03(327)(c) (c) The non-fixed contamination plus the fixed contamination on the inaccessible surface averaged over 300 cm2 (or the area of the surface if less than 300 cm2) does not exceed 8x105 Bq/cm2 (20 microcurie/cm2) for beta and gamma and low toxicity alpha emitters, or 8x104 Bq/cm2 (2 microcurie/cm2) for all other alpha emitters.

DHS 157.03(328) (328) “Sealed source” means any radioactive material that is encased in a capsule designed to prevent leakage or escape of the radioactive material.

DHS 157.03(329) (329) “Sealed Source and Device Registry” or “SSDR” means the national registry that contains all the registration certificates, maintained by the NRC that summarize the radiation safety information for the sealed sources and devices and describe the licensing and use conditions approved for the product.

DHS 157.03(330) (330) “Secondary dose monitoring system” means a system that will terminate irradiation in the event of failure of the primary dose monitoring system.

DHS 157.03(331) (331) “Secondary protective barrier” means the material that attenuates stray radiation.

DHS 157.03(331g) (331g) “Security order” means any order that was issued by the NRC that required fingerprints and an FBI criminal history records check for access to any one of the following:

DHS 157.03(331g)(a) (a) Safeguards information.

DHS 157.03(331g)(b) (b) Safeguards information-modified handling.

DHS 157.03(331g)(c) (c) Risk significant material such as special nuclear material or large quantities of uranium hexafluoride.

DHS 157.03(331m) (331m) “Security screening unit” means a non-human use open-beam or cabinet x-ray system with accessible openings designed for the detection of weapons, bombs, or contraband concealed in baggage, mail, packages or other commodities or structure.

DHS 157.03(331r) (331r) “Security zone” means any temporary or permanent area established by the licensee for the physical protection of category 1 or category 2 quantities of radioactive material.

DHS 157.03(332) (332) “Self-contained breathing apparatus” or “SCBA” means an atmosphere-supplying respirator for which the breathing air source is designed to be carried by the user.

DHS 157.03(333) (333) “Shadow tray” means a device attached to the radiation head to support auxiliary beam blocking material.

DHS 157.03(334) (334) “Shallow dose equivalent” or “Hs” means the dose equivalent at a tissue depth of 0.007 centimeter (7 mg/cm2). “Shallow dose equivalent” applies to the external exposure of the skin of the whole body or the skin of an extremity.

DHS 157.03(335) (335) “SI” means the abbreviation for the International System of Units.

DHS 157.03(336) (336) “Shielded position” means the location within the radiographic exposure device, source changer or storage container that, by manufacturer’s design, is the proper location for storage of the sealed source.

DHS 157.03(336m) (336m) 

DHS 157.03(336m)(a) (a) “Shielded room” means a room housing a radiation generating device where, with the device at maximum technique factors, the exterior room environs meets the unrestricted area dose limits of 0.02 mSv (2 mrem) in any one hour and 1 mSv (100 mrem) in a year at 30 cm from the surface of the barrier.

DHS 157.03(336m)(b) (b) “Shielded room” does not include any of the following:

DHS 157.03(336m)(b)1. 1. A radiation generating device that meets the definition of cabinet x-ray system.

DHS 157.03(336m)(b)2. 2. A permanent radiographic installation.

DHS 157.03(336m)(b)3. 3. A radiation room.

DHS 157.03(337) (337) “Shutter” means a device attached to the tube housing assembly which may totally intercept the useful beam and which has a lead equivalency not less than that of the tube housing assembly.

DHS 157.03(338) (338) “Sievert” or “Sv” means the SI unit of dose equivalent. The unit of dose equivalent is the joule per kilogram. The special unit of dose equivalent (rem) is being replaced by the sievert. 1 Sv=100 rem.

DHS 157.03(339) (339) “Single tomogram system” means a CT x-ray system which obtains x-ray transmission data during a scan to produce a single tomogram.

DHS 157.03(340) (340) “Site area emergency” means an event may occur, is in progress, or has occurred that could lead to a significant release of radioactive material and require a response by offsite response organizations to protect people offsite.

DHS 157.03(341) (341) “Site boundary” means that line beyond which the land or property is not owned, leased or otherwise controlled by the licensee or registrant.

DHS 157.03(342) (342) “Source” means the region and material from which the radiation emanates.

DHS 157.03(343) (343) “Source applicator” means a device used to place a radioactive source in a precise anatomical location within the body.

DHS 157.03(344) (344) “Source assembly” means an assembly that consists of the sealed source and a connector that attaches the source to the control cable. The source assembly may include a ballstop to secure the source in the shielded position.

DHS 157.03(345) (345) “Source changer” means a device designed and used for replacement of sealed sources in radiographic exposure devices and which may also be used for transporting and storing sealed sources.

DHS 157.03(346) (346) “Source holder” means a housing or assembly into which a radioactive source is placed to facilitate the handling and use of the source in well logging operations.

DHS 157.03(347) (347) “Source-image receptor distance” or “SID” means the distance from the source of radiation to the center of the input surface of the image receptor.

DHS 157.03(348) (348) “Source material” means either of the following:

DHS 157.03(348)(a) (a) Uranium or thorium, or any combination thereof, in any physical or chemical form.

DHS 157.03(348)(b) (b) Ores that contain by weight one-twentieth of one percent or more of uranium, thorium or any combination of uranium and thorium. Source material does not include special nuclear material.

DHS 157.03(349) (349) “Special form radioactive material” means radioactive material that satisfies all the following conditions:

DHS 157.03(349)(a) (a) It is either a single solid piece or is contained in a sealed capsule that may be opened only by destroying the capsule.

DHS 157.03(349)(b) (b) The piece or capsule has at least one dimension not less than 5 millimeters (0.2 in.).

DHS 157.03(349)(c) (c) It satisfies the test requirements specified by the NRC in 10 CFR 71.75 at the time of its design or construction.

DHS 157.03(350) (350) “Special nuclear material” means plutonium, uranium 233, uranium enriched in the isotope 233 or in the isotope 235, and any other material which the nuclear regulatory commission determines to be special nuclear material; or any material artificially enriched by any of the foregoing. Special nuclear material does not include source material.

DHS 157.03(351) (351) “Special nuclear material in quantities not sufficient to form a critical mass” means uranium enriched in the isotope U-235 in quantities not exceeding 350 grams of contained U-235; uranium-233 in quantities not exceeding 200 grams; plutonium in quantities not exceeding 200 grams; or any combination of them under the following formula: For each kind of special nuclear material, determine the ratio between the quantity of that special nuclear material and the quantity specified above for the same kind of special nuclear material. The sum of such ratios for all of the kinds of special nuclear material in combination may not exceed one.

DHS 157.03 Note Note: For example, the following quantities in combination would not exceed the limitation and are within the formula:

DHS 157.03 Note 175 (grams contained U-235) + 50 (grams U-233) + 50 (grams Pu) = 1

DHS 157.03 Note   350   200   200

DHS 157.03(352) (352) “Special unit” means the alternative system of units for quantifying absorbed dose in rad, dose equivalent in rem and radioactivity in curie.

DHS 157.03(353) (353) “Specific activity” of a radionuclide means the radioactivity of the radionuclide per unit mass of that nuclide. The specific activity of a material in which the radionuclide is essentially uniformly distributed is the radioactivity per unit mass of the material.

DHS 157.03(354) (354) “Specific license” means a license, under requirements prescribed by the department by rule, to possess, use, manufacture, produce, transfer or acquire radioactive material or devices or equipment utilizing radioactive material.

DHS 157.03(355) (355) “Spot film” means a radiograph, which is made during a fluoroscopic examination to permanently record conditions that exist during that fluoroscopic procedure.

DHS 157.03(356) (356) “Spot-film device” means a device intended to transport and position a radiographic image receptor between an x-ray source and fluoroscopic image receptor. It includes a device intended to hold a cassette over the input end of an image intensifier for the purpose of making a radiograph.

DHS 157.03(357) (357) “Stationary beam radiation therapy” means radiation therapy without displacement of one or more mechanical axes relative to the patient during irradiation.

DHS 157.03(358) (358) “Stationary x-ray equipment” means x-ray equipment that is installed in a fixed location.

DHS 157.03(359) (359) “Stereotactic radiosurgery” means the use of external radiation in conjunction with a stereotactic guidance device to deliver a dose to a tissue volume from multiple sources of radiation simultaneously.

DHS 157.03(360) (360) “Stochastic effect” means a health effect that occurs randomly and for which the probability of the effect occurring, rather than its severity, is assumed to be a linear function of dose without threshold. Hereditary effects and cancer incidence are examples of stochastic effects.

DHS 157.03(361) (361) “Storage area” means any secure location, facility or vehicle that is used to store and secure a radiographic exposure device, a radiation machine, a storage container or a sealed source, when it is not in use.

DHS 157.03(362) (362) “Storage container” means a device in which sealed sources or radiation machines are secured and stored.

DHS 157.03(363) (363) “Stray radiation” means the sum of leakage and scattered radiation.

DHS 157.03(364) (364) “Structured educational program” means an educational program designed to impart particular knowledge and practical education through interrelated studies and supervised training.

DHS 157.03(365) (365) “S-tube” means a tube through which the radioactive source travels when inside a radiographic exposure device.

DHS 157.03(366) (366) “Subsurface” means below the surface of the earth.

DHS 157.03(367) (367) “Subsurface tracer study” means the release of a substance tagged with radioactive material to trace the movement or position of the tagged substance in the well-bore or adjacent formation.

DHS 157.03(368) (368) “Supplied-air respirator” or “SAR” means an atmosphere-supplying respirator for which the source of breathing air is not designed to be carried by the user.

DHS 157.03(369) (369) “Surface casing for protecting fresh water aquifers” means a pipe or tube used as a lining in a well to isolate fresh water aquifers from the well.

DHS 157.03(370) (370) “Surface contaminated object” or “SCO” means a solid object that is not itself classed as radioactive material, but which has radioactive material distributed on any of its surfaces.

DHS 157.03(371) (371) “Survey” means an evaluation of the radiological conditions and potential hazards incident to the production, use, transfer, release, disposal or presence of sources of radiation. When appropriate, an evaluation includes tests, physical examinations and measurements of levels of radiation or concentrations of radioactive material present.

DHS 157.03(371m) (371m) “Tailing” means the residual material resulting from the extraction of minerals from the earth.

DHS 157.03(372) (372) “Target” means that part of an x-ray tube or accelerator onto which a beam of accelerated particles is directed to produce ionizing radiation or other particles.

DHS 157.03(373) (373) “Target-skin distance” or “TSD” means the distance measured along the beam axis from the center of the front surface of the x-ray target or electron virtual source to the surface of the irradiated object or patient.

DHS 157.03(374) (374) “Technique factors” means the following conditions of operation:

DHS 157.03(374)(a) (a) For capacitor energy storage equipment, peak tube potential in kV and quantity of charge in mAs.

DHS 157.03(374)(b) (b) For field emission equipment rated for pulsed operation, peak tube potential in kV and number of x-ray pulses.

DHS 157.03(374)(c) (c) For CT equipment designed for pulsed operation, peak tube potential in kV, scan time in seconds, and either tube current in milliamperes (mA), x-ray pulse width in milliseconds, and the number of x-ray pulses per scan; or the product of tube current, x-ray pulse width, and the number of x-ray pulses per scan expressed as mAs.

DHS 157.03(374)(d) (d) For CT x-ray equipment not designed for pulsed operation, peak tube potential in kV, and either tube current in mA and scan time in seconds, or the product of tube current and exposure time in mAs and the scan time when the scan time and exposure time are equivalent.

DHS 157.03(374)(e) (e) For all other equipment, peak tube potential in kV and either tube current in mA and exposure time in seconds or the product of tube current and exposure time in mAs.

DHS 157.03(374m) (374m) “Telemetric position monitoring system” means a data transfer system that captures information by instrumentation or measuring devices about the location and status of a transport vehicle or package between the departure and destination locations.

DHS 157.03(375) (375) “Teletherapy” means a method of radiation therapy in which collimated gamma rays are delivered from a source at a distance from the patient or human research subject.

DHS 157.03(376) (376) “Temporary job site” means a location where any of the following occur:

DHS 157.03(376)(a) (a) Radiographic operations are performed and sources of radiation may be stored other than at the location or locations of use authorized on the license or registration.